Method of and apparatus for heat treating parts



Dec. 2, 1958 w. E. ENGELHARD METHOD OF AND APPARATUS FOR HEAT TREATING PARTS Filed June 1, 1956 2 Sheets-Sheet 1 INVENTOR.

ATTORNEY Dec. 2, 1958 w ENGELHARD 2,862,843

METHOD OF AND APPARATUS F OR HEAT TREATING PARTS Filed June 1, 1956 2 Sheets-Sheet 2 1 -5 T1 .E. MT {4 I I M EW I) II 1 United States Patent METHOD or AND APPARATUS FOR HEAT TREATING PARTS William E. Engelhard, Apalachin, N. Y. Application June 1, 1956, Serial No. 588,866

9 Claims. (Cl. 14821.55)

This invention relates to the art of heat treating parts to impart hardness thereto, by initially heating them to predetermined elevated temperature, and then cooling said parts. In the past great difliculty has been experienced in the heat treating of metal parts, for example, which vary in size, dimensions or cross-sectionally. Such variations are, as a practical matter, the rule rather than the exception and the difiiculty is a serious one. Smaller parts tended to cool more rapidly than larger parts, and parts having non-uniform cross-sections cooled unevenly, resulting in warpage, cracking, distortion and variations in the structural characteristics of the treated parts.

Many efforts have been made to overcome the difliculties mentioned, but procedures proposed for solving the problem frequently resulted in creating new problems, such as that of the subsequent removal of tenaciouslyadhering quenching media, or special handling problems requiring critical controls and generally providing time consuming, expensive, unsatisfactory and non-uniform results. The problem is one of long standing in the art.

' In the method and apparatus of my invention, as set forth herein, the problem is solved by the provision of unique means for first exposing previously heated parts to the full heat-dissipating value of a complete volume of quenching media, thereby rapidly cooling the parts and, then sealing the parts within an enveloping shield enclosing a fractional volume of the quenching media. The enclosed media, having reached an elevated temperature by absorption of heat from the rapidly cooled parts, is then of approximately the same temperature as the parts so that the further cooling of the parts by heat transfer occurs at a very slow rate. This phase of slow rate of further heat dissipation of the parts provides a highly desirable final progressive cooling stage, or stages, which, in practice, enables thicker and thinner sections of a part and parts of different characteristics and sizes to cool slowly and uniformly, eliminating cracking, warpage, and distortion which would occur if the final cooling stage were rapid, and enabling the parts to complete the cooling cycle without structural stress and strain.

In the drawings:

Fig. 1 is a broken, vertical, sectional view, showing the work with the protective shield thereover about to be immersed in a quenching tank,

'Fig. 2 is a similar view, showing the work initially immersed, the protective shield being held away from the work parts by the expanding gasses generated in the initial immersion of the parts in the quenching medium,

Fig. 3 is a similar view, the work having dropped down to or near the bottom of the quenching medium tank, carrying the protective shield with it from the time of contact of the stop member on the rod 17 attached to the work platform 16 with said shield,

Fig. 4 is a similar view, but showing the protective v 2 shield fully descended and returned to its position over the work on termination of the gas generation phase,

Fig. 5 is a vertical sectional view of another form of) apparatus for carrying out the invention, and

Fig. 6 is a fragmentary, elevational view of a further form thereof. I

As shown in the drawings, the method of this inven-- tion is directed to the heat treatment of parts, such as, for example, shown at 10 in Fig. 1, initially brought up to the desired degree of heat for hardening or other purposes by'suitable means (such as a furnace or other heating medium). The articles may be initially posi-' tioned on a holder 01' platform 16 (Fig. 1) having a carrier rod 17 secured thereto for facility of handling.

Pursuant to the invention, the heated parts are placed in a quenching tank 13 having a given volume of quench ing medium 14 extending to a given level 35 therein. A closure heat shield 18 (which may, for example, be in the form of an inverted cup, Fig. 3) normally rests, by its weight alone (weight may be added to theshield,

if desired), on the parts platform 16 in enveloping relation to the parts 10, and thus, with the platform, enclosesthe parts 10 initially (Fig. l) and in the final cooling stage (Fig. 4). Shield 18 is preferably slidably arranged (as noted at 20, Figs. 3 and 4) on the rod 17; a gasket cap 19 on the shield 18 encloses a gasket 12 which embraces the rod while maintaining the shield slidably thereon at all times.

The slidable connection 20 provides a restricted opening to slidably receive the rod 17, but it need not be gas tight. By varyingthe diameter of the opening in shield 18 or in the gasket 12 thereof slidably receiving rod 17 at point'20 one may vary the rate at or extent to which gases =built'up within the shield 18 may escape therefrom and thus the time interval required for the shield 18 to begin to descend of its own weight, as

provided with an extended arm 21 secured thereto and slidable in a guide bearing 22, which, in turn, may be secured to a suitable support or to a part such as a bracket 23 having rollers 24 riding on rails 25. A suitable hoist 26 may be rotably journalled on a shaft 27 of the bracket 23 and connected, as by cable 28, with a loop 29 at the upper end of arm 21. Thus the heat shield 18 will move away from and toward the work parts 10 in alignment therewith automatically during the gas generation phase and at the conclusion thereof as above mentioned. The work shield 18, in the Fig. 5 form, may fully rise, for example, to the position indicated by dotted line 31 in the intense gas generation phase and thereafter return to the full line position.

The following appears to be the modus operandi pursuant to the invention: The platform 16 and previously heated work positioned thereon is initially positioned in heated) is marked; gases and flame emanate from the work and a pronounced reaction occurs on immersion of the work in the tank and for a short time thereafter, 7

because of this diiference in temperature. The gases fill the interior of closure shield 18 and keep the shield up, away from the work, while the work descends with the continued lowering of rod 16 and thus for a time 5 fully exposed to heat exchange with the entire volume of the quenching medium 14. This rapidly cools the work; within a very short interval of time the work will be cooled to the degree desired for hardening.

Condensation of vapor on the underside of the top wall of the work shield 18 interiorly thereof occurs as the work cools, creating a vacuum which draws said shield downwardly and onto the work platform 16 (Fig. 4) so that the parts will be enveloped by the fractional part of the total volume of quenching medium which is within the area 33 in the shield 18. Thereafter, cooling of the work continues at a slower, but uniform rate, the medium 14 confined within the area. 33 and the work gradually cooling togethen'uniformly, the parts cooling slowly and uniformly and without cracking and warping.

Rod 17 may be provided with a stop member 11 (Fig. 3) so that as the platform 16 and work thereon descends to the bottom of the tank 13, the stop member 11 will contact the shield 18 and drawfit'partly downwardly with it. Stop 11 also prevents the shield from moving too far upwardly responsive to the generation of gases following the initial deposit of the platform and work (Fig. 1) in the quenching medium. If desired, the work shield may be moved downwardly ahead of the normal (Fig. 4) tendency thereof to automatically do so or may be delayed in descending. Thus, as in Fig. 5, the operator who may manually or otherwise operate a handle 30 secured to the shield 18 to that end; automatically operative means such as shown in Fig. 6 (illustrating one of many forms suitable to that end) may be provided. In the Fig. 6 form a thermostatic switch 40 is shown disposed within tank 13, and a relay 41 actuated thereby to energize a motor 42 whose armature shaft 44 may have an eccentric 45 keyed thereto to actuate a rod 43 connected to a stud 46 extending from the upper end of shield 18.

As above mentioned, pursuant to the invention, tank 13 is filled with a liquid medium 14 which is not preheated but is essentially at room temperature and is selected to boil (Fig. 3) to first expose the parts to the full volume of liquid medium 14 and then (Fig. 4) the member 18 descends and encloses the parts in a fraction of the original volume of liquid medium 14, to cool slowly.

The critical temperature to which the parts (Fig. 1) are pre-heated is well known in the industry and is recorded in many tables; it varies according to the particular type of steel of which the parts are made. Tables are readily available giving such data and the martensitic temperature range of the parts and therefore the quenching medium which should be placed in tank 14 for such parts (for boiling in the desired temperature range). Such information is readily available by reference, for example, to such standard works as the 1948 edition of Metals Handbook published by the ASM, note particularly pages 607-612 thereof.

I claim:

1. The method of cooling parts which have been heat treated to critical temperatures and positioned on a holder, which consists of positioning a quenching medium of substantially lower temperature than that to which the parts have been heated, in a tank, immersing said parts and holder in said tank, immersing an inverted U-shaped shield in said tank in line with said parts and holder, aligning said shield for vertical movement in said line with said parts, said parts on their said immersion insaid quenching medium generating gases which rise and flow into said aligned shield, holding the shield spaced above the parts with the parts immersed in and exposed to the quenching medium in the tank, said parts then rapidly cooling, terminating their generation of gases, said shield then moving downwardly over the parts and holder, enclosing the parts and the surrounding quenching medium within the shield, and maintaining the parts and surrounding quenching medium within the shield for cooling together while thus within the shield.

face of the quenching medium.

4. The method of cooling parts which have been heat treated to critical temperatures, which consists of positioning liquid quenching medium, of substantially lower temperature than that to which the parts have been so heat treated, in a tank having an open top, positioning said parts in the liquid medium in the tank, positioning a substantially inverted U-shaped shield in said tank through said open top, above and in line with the parts but below the level of the quenching medium, said parts being thus exposed to heat transfer action with the full volume of quenching medium in the tank, said shield then moving downwardly in the tank and over said parts and enclosing the parts and surrounding medium within the shield, for cooling of the parts in contact with the medium so confined within the shield, and limiting the extent of movement of the shield away from the parts, to prevent movement of the shield out of the surface of the quenching medium.

5. The method of cooling parts, which have been heat treated to critical temperatures, in a tank having anopen upper end and having a quenching medium of substantially lower temperature than that to which the parts have been heated, which consists of immersing said parts in the quenching medium in the tank, positioning an inverted U-shaped shield in said tank through said open end of the tank, aligning said shield for free, vertical movement in the liquid medium in said tank below the open end of the tank and relative to the parts, said parts on their said immersion in said quenching medium generating gases which rise and flow into said shield, holding the shield Spaced above the parts with the parts immersed in and exposed to the quenching medium in the tank, said parts then rapidly cooling, terminating their generation of gases, said shield then moving downwardly over the parts, enclosing the parts and the surrounding quenching medium within the shield, and maintaining the parts and surrounding quenching medium within the shield for cooling together while thus within the shield.

6. In the method of cooling parts as set forth in claim 5, the further step which consists of limiting the extent of movement of the shield away from the parts to prevent movement of the shield out of the quenching medium in the tank.

7. An apparatus for cooling parts which have been heat treated to critical temperatures and positioned on a holder, comprising a tank open at the top, adapted to receive a quenching medium, a substantially inverted U- shaped shield, guide means on said holder engaging said shield for aligning the shield for vertical movement in line with and away from said parts so that, on initial immersion of said parts in said quenching medium, gases generated on contact of said parts with said quenching medium will pass upwardly into the shield and hold the shield away from said parts, so that the latter will be exposed to heat transfer action with the full volume of quenching medium in the tank, means engaging the shield for moving the shield, and temperature responsive means in the tank for actuating the means engaging the hield at a given temperature.

8. An apparatus for cooling parts which have been heat treated to critical temperatures and positioned on a holder, comprising a tank, having an open top, said tank adapted to receive a quenching medium of substantially lower temperature than that to which the parts have been heat treated, into which quenching medium said holder and parts may be deposited, a shield comprising a bottom portion and a wall member extending from the bottom portion and defining therewith a U-shape, and having an aperture in the bottom thereof, means secured to the holder and passing through the apertured bottom of the shield, slidably aligning the shield relative to the holder, said means so extending through said shield and substantially thereabove through the quenching medium and through the open top of the tank, slidably aligning the shield for free movement, in the quenching medium, between the holder in the tank and the top of the tank, said parts, on their said immersion in said quenching medium, generating gase which rise and flow into said shield, holding the shield spaced above the parts, said parts then rapidly cooling, terminating their generation of gases, said shield then moving downwardly over the parts, enclosing the parts and the surrounding quenching medium within the shield, and maintaining the parts and surrounding quenching medium within the shield for cooling together while thus within the shield, a stop member on said aligning means, spaced from the holder a lesser distance than the height of the tank, preventing movement of the shield out of the surface of the quenching medium.

9. An apparatus for cooling parts which have been heat treated to critical temperatures, comprising a tank open at the top, adapted to receive a quenching medium, a shield comprising a bottom portion and a wall member extending therefrom and defining therewith an essentially U-shaped member having an aperture in the bottom thereof, means in the tank passing through said aperture slidably aligning the shield relative to the parts, one end of said means so passing through said shield, extending through the quenching medium and through the open top of the tank, slidably aligning the shield for free movement, in the quenching medium, between the parts in the tank and the top of the tank, said parts on their said immersion in said quenching medium generating gases which rise and flow into said shield, holding the shield spaced above the parts with the parts immersed in and exposed to the quenching medium in the tank, said parts then rapidly cooling, terminating their generation of gases, said shield then moving downwardly over the parts, enclosing the parts and the surrounding quenching medium within the shield, and maintaining the parts and surrounding quenching medium within the shield for cooling together while thus within the shield, a stop member on said aligning means, spaced from the other end of the aligning means a lesser distance than the height of the tank, preventing movement of the shield out of the surface of the quenching medium.

References Cited in the file of this patent UNITED STATES PATENTS Walter May 13, 1919 

1. THE METHOD OF COOLING PARTS WHICH HAVE BEEN HEAT TREATED TO CRITICAL TEMPERATURES AND POSITIONED ON A HOLDER, WHICH CONSISTS OF POSITIONING A QUENCHING MEDIUM OF SUBSTANTIALLY LOWER TEMPERATURE THAN THAT TO WHICH THE PARTS HAVE BEEN HEATED, IN A TANK, IMMERSING SAID PARTS AND HOLDER IN SAID TANK, IMMERSING AN INVERTED U-SHAPED SHIELD IN SAID TANK IN LINE WITH SAID PARTS AND HOLDER, ALIGNING SAID SHIELDS FOR VERTICAL MOVEMENT IN SAID LINE WITH SAID PARTS, SAID PARTS ON THEIR SAID IMMERSION IN SAID QUENCHING MEDIUM GENERATING GASES WHICH RISE AND FLOW INTO SAID ALIGNED SHIELD, HOLDING THE SHIELD SPACED ABOVE THE PARTS WITH THE PARTS IMMERSED IN AND EXPOSED TO THE QUENCHING MEDIUM IN THE TANK, SAID PARTS THEN RAPIDLY COOLING, TERMINATING THEIR GENERATION OF GASES, SAID SHIELD THEN MOVING DOWNWARDLY OVER THE PARTS AND HOLDER, ENCLOSING THE PARTS AND THE SURROUNDING QUENCHING MEDIUM WITHIN THE SHIELD, AND MAINTAINING THE PARTS AND SURROUNDING QUENCHING MEDIUM WITHIN THE SHIELD FOR COOLING TOGETHER WHILE THUS WITHIN THE SHIELD.
 4. THE METHOD OF COOLING PARTS WHICH HAVE BEEN HEAT TREATED TO CRITICAL TEMPERATURES, WHICH CONSISTS OF POSITIONING LIQUID QUENCHING MEDIUM, OF SUBSTANTIALLY LOWER TEMPERATURE THAN THAT TO WHICH THE PARTS HAVE BEEN SO HEAT TREATED, IN A TANK HAVING ON OPEN TOP, POSITIONING SAID PARTS IN THE LIQUID MEDIUM IN THE TANK, POSITIONING A SUBSTANTIALLY INVERTED U-SHAPED SHIELD IN SAID TANK THROUGH SAID OPEN TOP, ABOVE AND IN LINE WITH THE PARTS BUT BELOW THE LEVEL OF THE QUENCHING MEDIUM, SAID PARTS BEING THUS EXPOSED TO HEAT TRANSFER ACTION WITH THE FULL VOLUME OF QUENCHING MEDIUM IN THE TANK, SAID SHIELD THEN MOVING DOWNWARDLY IN THE TANK AND OVER SAID PARTS AND ENCLOSING THE PARTS AND SURROUNDING MEDIUM WITHIN THE SHIELD, FOR COOLING OF THE PARTS IN CONTACT WITH THE MEDIUM SO CONFINED WITHIN THE SHIELD, AND LIMITING THE EXTENT OF MOVEMENT OF THE SHIELD AWAY FROM THE PARTS, TO PREVENT MOVEMENT OF THE SHIELD OUT OF THE SURFACE OF THE QUENCHING MEDIUM. 